1 //===--- Ownership.h - Parser ownership helpers -----------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file contains classes for managing ownership of Stmt and Expr nodes.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_SEMA_OWNERSHIP_H
15 #define LLVM_CLANG_SEMA_OWNERSHIP_H
16 
17 #include "clang/Basic/LLVM.h"
18 #include "llvm/ADT/ArrayRef.h"
19 #include "llvm/ADT/PointerIntPair.h"
20 
21 //===----------------------------------------------------------------------===//
22 // OpaquePtr
23 //===----------------------------------------------------------------------===//
24 
25 namespace clang {
26   class CXXCtorInitializer;
27   class CXXBaseSpecifier;
28   class Decl;
29   class Expr;
30   class ParsedTemplateArgument;
31   class QualType;
32   class Stmt;
33   class TemplateName;
34   class TemplateParameterList;
35 
36   /// \brief Wrapper for void* pointer.
37   /// \tparam PtrTy Either a pointer type like 'T*' or a type that behaves like
38   ///               a pointer.
39   ///
40   /// This is a very simple POD type that wraps a pointer that the Parser
41   /// doesn't know about but that Sema or another client does.  The PtrTy
42   /// template argument is used to make sure that "Decl" pointers are not
43   /// compatible with "Type" pointers for example.
44   template <class PtrTy>
45   class OpaquePtr {
46     void *Ptr;
OpaquePtr(void * Ptr)47     explicit OpaquePtr(void *Ptr) : Ptr(Ptr) {}
48 
49     typedef llvm::PointerLikeTypeTraits<PtrTy> Traits;
50 
51   public:
OpaquePtr()52     OpaquePtr() : Ptr(nullptr) {}
53 
make(PtrTy P)54     static OpaquePtr make(PtrTy P) { OpaquePtr OP; OP.set(P); return OP; }
55 
56     /// \brief Returns plain pointer to the entity pointed by this wrapper.
57     /// \tparam PointeeT Type of pointed entity.
58     ///
59     /// It is identical to getPtrAs<PointeeT*>.
getPtrTo()60     template <typename PointeeT> PointeeT* getPtrTo() const {
61       return get();
62     }
63 
64     /// \brief Returns pointer converted to the specified type.
65     /// \tparam PtrT Result pointer type.  There must be implicit conversion
66     ///              from PtrTy to PtrT.
67     ///
68     /// In contrast to getPtrTo, this method allows the return type to be
69     /// a smart pointer.
getPtrAs()70     template <typename PtrT> PtrT getPtrAs() const {
71       return get();
72     }
73 
get()74     PtrTy get() const {
75       return Traits::getFromVoidPointer(Ptr);
76     }
77 
set(PtrTy P)78     void set(PtrTy P) {
79       Ptr = Traits::getAsVoidPointer(P);
80     }
81 
82     explicit operator bool() const { return Ptr != nullptr; }
83 
getAsOpaquePtr()84     void *getAsOpaquePtr() const { return Ptr; }
getFromOpaquePtr(void * P)85     static OpaquePtr getFromOpaquePtr(void *P) { return OpaquePtr(P); }
86   };
87 
88   /// UnionOpaquePtr - A version of OpaquePtr suitable for membership
89   /// in a union.
90   template <class T> struct UnionOpaquePtr {
91     void *Ptr;
92 
makeUnionOpaquePtr93     static UnionOpaquePtr make(OpaquePtr<T> P) {
94       UnionOpaquePtr OP = { P.getAsOpaquePtr() };
95       return OP;
96     }
97 
getUnionOpaquePtr98     OpaquePtr<T> get() const { return OpaquePtr<T>::getFromOpaquePtr(Ptr); }
99     operator OpaquePtr<T>() const { return get(); }
100 
101     UnionOpaquePtr &operator=(OpaquePtr<T> P) {
102       Ptr = P.getAsOpaquePtr();
103       return *this;
104     }
105   };
106 }
107 
108 namespace llvm {
109   template <class T>
110   class PointerLikeTypeTraits<clang::OpaquePtr<T> > {
111   public:
getAsVoidPointer(clang::OpaquePtr<T> P)112     static inline void *getAsVoidPointer(clang::OpaquePtr<T> P) {
113       // FIXME: Doesn't work? return P.getAs< void >();
114       return P.getAsOpaquePtr();
115     }
getFromVoidPointer(void * P)116     static inline clang::OpaquePtr<T> getFromVoidPointer(void *P) {
117       return clang::OpaquePtr<T>::getFromOpaquePtr(P);
118     }
119     enum { NumLowBitsAvailable = 0 };
120   };
121 
122   template <class T>
123   struct isPodLike<clang::OpaquePtr<T> > { static const bool value = true; };
124 }
125 
126 namespace clang {
127   // Basic
128   class DiagnosticBuilder;
129 
130   // Determines whether the low bit of the result pointer for the
131   // given UID is always zero. If so, ActionResult will use that bit
132   // for it's "invalid" flag.
133   template<class Ptr>
134   struct IsResultPtrLowBitFree {
135     static const bool value = false;
136   };
137 
138   /// ActionResult - This structure is used while parsing/acting on
139   /// expressions, stmts, etc.  It encapsulates both the object returned by
140   /// the action, plus a sense of whether or not it is valid.
141   /// When CompressInvalid is true, the "invalid" flag will be
142   /// stored in the low bit of the Val pointer.
143   template<class PtrTy,
144            bool CompressInvalid = IsResultPtrLowBitFree<PtrTy>::value>
145   class ActionResult {
146     PtrTy Val;
147     bool Invalid;
148 
149   public:
150     ActionResult(bool Invalid = false)
151       : Val(PtrTy()), Invalid(Invalid) {}
152     ActionResult(PtrTy val) : Val(val), Invalid(false) {}
153     ActionResult(const DiagnosticBuilder &) : Val(PtrTy()), Invalid(true) {}
154 
155     // These two overloads prevent void* -> bool conversions.
156     ActionResult(const void *);
157     ActionResult(volatile void *);
158 
159     bool isInvalid() const { return Invalid; }
160     bool isUsable() const { return !Invalid && Val; }
161     bool isUnset() const { return !Invalid && !Val; }
162 
163     PtrTy get() const { return Val; }
164     template <typename T> T *getAs() { return static_cast<T*>(get()); }
165 
166     void set(PtrTy V) { Val = V; }
167 
168     const ActionResult &operator=(PtrTy RHS) {
169       Val = RHS;
170       Invalid = false;
171       return *this;
172     }
173   };
174 
175   // This ActionResult partial specialization places the "invalid"
176   // flag into the low bit of the pointer.
177   template<typename PtrTy>
178   class ActionResult<PtrTy, true> {
179     // A pointer whose low bit is 1 if this result is invalid, 0
180     // otherwise.
181     uintptr_t PtrWithInvalid;
182     typedef llvm::PointerLikeTypeTraits<PtrTy> PtrTraits;
183   public:
184     ActionResult(bool Invalid = false)
185       : PtrWithInvalid(static_cast<uintptr_t>(Invalid)) { }
186 
187     ActionResult(PtrTy V) {
188       void *VP = PtrTraits::getAsVoidPointer(V);
189       PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
190       assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
191     }
192     ActionResult(const DiagnosticBuilder &) : PtrWithInvalid(0x01) { }
193 
194     // These two overloads prevent void* -> bool conversions.
195     ActionResult(const void *);
196     ActionResult(volatile void *);
197 
198     bool isInvalid() const { return PtrWithInvalid & 0x01; }
199     bool isUsable() const { return PtrWithInvalid > 0x01; }
200     bool isUnset() const { return PtrWithInvalid == 0; }
201 
202     PtrTy get() const {
203       void *VP = reinterpret_cast<void *>(PtrWithInvalid & ~0x01);
204       return PtrTraits::getFromVoidPointer(VP);
205     }
206     template <typename T> T *getAs() { return static_cast<T*>(get()); }
207 
208     void set(PtrTy V) {
209       void *VP = PtrTraits::getAsVoidPointer(V);
210       PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
211       assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
212     }
213 
214     const ActionResult &operator=(PtrTy RHS) {
215       void *VP = PtrTraits::getAsVoidPointer(RHS);
216       PtrWithInvalid = reinterpret_cast<uintptr_t>(VP);
217       assert((PtrWithInvalid & 0x01) == 0 && "Badly aligned pointer");
218       return *this;
219     }
220 
221     // For types where we can fit a flag in with the pointer, provide
222     // conversions to/from pointer type.
223     static ActionResult getFromOpaquePointer(void *P) {
224       ActionResult Result;
225       Result.PtrWithInvalid = (uintptr_t)P;
226       return Result;
227     }
228     void *getAsOpaquePointer() const { return (void*)PtrWithInvalid; }
229   };
230 
231   /// An opaque type for threading parsed type information through the
232   /// parser.
233   typedef OpaquePtr<QualType> ParsedType;
234   typedef UnionOpaquePtr<QualType> UnionParsedType;
235 
236   // We can re-use the low bit of expression, statement, base, and
237   // member-initializer pointers for the "invalid" flag of
238   // ActionResult.
239   template<> struct IsResultPtrLowBitFree<Expr*> {
240     static const bool value = true;
241   };
242   template<> struct IsResultPtrLowBitFree<Stmt*> {
243     static const bool value = true;
244   };
245   template<> struct IsResultPtrLowBitFree<CXXBaseSpecifier*> {
246     static const bool value = true;
247   };
248   template<> struct IsResultPtrLowBitFree<CXXCtorInitializer*> {
249     static const bool value = true;
250   };
251 
252   typedef ActionResult<Expr*> ExprResult;
253   typedef ActionResult<Stmt*> StmtResult;
254   typedef ActionResult<ParsedType> TypeResult;
255   typedef ActionResult<CXXBaseSpecifier*> BaseResult;
256   typedef ActionResult<CXXCtorInitializer*> MemInitResult;
257 
258   typedef ActionResult<Decl*> DeclResult;
259   typedef OpaquePtr<TemplateName> ParsedTemplateTy;
260 
261   typedef MutableArrayRef<Expr*> MultiExprArg;
262   typedef MutableArrayRef<Stmt*> MultiStmtArg;
263   typedef MutableArrayRef<ParsedTemplateArgument> ASTTemplateArgsPtr;
264   typedef MutableArrayRef<ParsedType> MultiTypeArg;
265   typedef MutableArrayRef<TemplateParameterList*> MultiTemplateParamsArg;
266 
267   inline ExprResult ExprError() { return ExprResult(true); }
268   inline StmtResult StmtError() { return StmtResult(true); }
269 
270   inline ExprResult ExprError(const DiagnosticBuilder&) { return ExprError(); }
271   inline StmtResult StmtError(const DiagnosticBuilder&) { return StmtError(); }
272 
273   inline ExprResult ExprEmpty() { return ExprResult(false); }
274   inline StmtResult StmtEmpty() { return StmtResult(false); }
275 
276   inline Expr *AssertSuccess(ExprResult R) {
277     assert(!R.isInvalid() && "operation was asserted to never fail!");
278     return R.get();
279   }
280 
281   inline Stmt *AssertSuccess(StmtResult R) {
282     assert(!R.isInvalid() && "operation was asserted to never fail!");
283     return R.get();
284   }
285 }
286 
287 #endif
288